1. Field of the Invention
The present invention relates to the formation of a polysilicon layer, and more particularly to a method for the formation of polysilicon layer by irradiating with intermittently conducting Si.sub.2 H.sub.6 gas process on a silicon substrate layer of silicon wafer for a semiconductor.
2. Description of the Prior Art
Currently, the demand for high-density dynamic random access memory (DRAM) has rapily increased due to the widespread use of electronic equipment. In particular, the increasing popularity of some electronic equipment such as, for example, many kinds of computers are gradually increasing the demand for the large or very large semiconductor memories. Therefore, the advanced manufacture technology for improvement fabrication of DRAm is urgently needed.
No doubt one of the main technologies for improving DRAM performance is the Hemi-Spherical Grain (HSG) process. In fact, the recently Hemi-Spherical Grain (HSG) process is gradually applied to the production technology of High-Density DRAM. Futhermore, HSG process ideally will increase the surface area of the silicon layer in order to expand the capacity of the DRAM. This issue has been presented by previous laboratory experience already.
Basically, the HSG process firstly involves the deposit of an alpha-silicon thin film on the substrate of silicon wafer inside a PCVD furnace at 1 torr and 510.degree.C to 550.degree.C. Consequentially, the alpha-Silicon film surface is cleaned using SC-1 wet cleaning and then the native oxide layer is removed by HF dipping. Afterwards, HSG will grow in the UHV-CVD system chamber. When the wafer is irradiated for about 60 seconds, gas is conducted into the chamber. At this step, the temperature is arrived at about 200.degree.C to 300.degree.C as shown in FIG. 1A, then the flow of gas ceases after about 60 seconds. Thirdly, the temperature is held at 600.degree.C. The whole treatment time is about 300 seconds at least. The pressure is about 10.sup.-5 torr when the gas is being conducted into the chamber. Also, when the gas is not conducted into the chamber, the pressure will be about 10.sup.-8 torr as shown FIG. 1B. Also the flow of the gas fluid is about 10 sccm.
However, unfortunately the HSG process is still not totally desirable because it usually will take a long time for treating each wafer. On the other hand, it is still necessary to be refined again. Accordingly, the present invention presents a brand new preferred method.